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test_sizeof

news 2025/8/22 6:16:20

test_sizeof

//结论：
// sizeof(arrU8)得到的大小是u8类型数组的 **定义大小**，在 初始化的时候用
// strlen(arrU8)得到的大小是u8类型数组的 **实际大小**，在复制的时候用
//sizeof((char*)arrU8)，把一个u8 * 转成 char *，在32位机器上结果是4,64位机器上是8
//sizeof((char*)arrU8)是输出一个指针的大小
//要打印u8类型的数组，直接arrU8就可以了，不用加(char*);

#include <stdio.h>
#include <stdlib.h>
#include <string.h>typedef unsigned char u8;int main(void)
{u8 arrU8[12] = {0};printf("printf arrU8[12] by arrU8 = %s\n", arrU8);//printf arrU8[12] by arrU8 = printf("printf arrU8[12] by (char*)arrU8=%s\n", (char*)arrU8);//printf arrU8[12] by (char*)arrU8=printf("sizeof(arrU8)=%d\n", sizeof(arrU8));//sizeof(arrU8)=12printf("sizeof((char*)arrU8)=%d\n", sizeof((char*)arrU8));//sizeof((char*)arrU8)=8printf("strlen(arrU8)=%d\n", strlen(arrU8));//strlen(arrU8)=0printf("strlen((char*)arrU8)=%d\n", strlen((char*)arrU8));//strlen((char*)arrU8)=0memcpy(arrU8, "123456789", 9);printf("---------------------------------------------\n");printf("printf arrU8[12] by arrU8 = %s\n", arrU8);//printf arrU8[12] by arrU8 = 123456789printf("printf arrU8[12] by (char*)arrU8=%s\n", (char*)arrU8);//printf arrU8[12] by (char*)arrU8=123456789printf("sizeof(arrU8)=%d\n", sizeof(arrU8));//sizeof(arrU8)=12printf("sizeof((char*)arrU8)=%d\n", sizeof((char*)arrU8));//sizeof((char*)arrU8)=8printf("strlen(arrU8)=%d\n", strlen(arrU8));//strlen(arrU8)=9printf("strlen((char*)arrU8)=%d\n", strlen((char*)arrU8));//strlen((char*)arrU8)=9//结论：//sizeof(arrU8)得到的大小是u8类型数组的定义大小//strlen(arrU8)得到的大小是u8类型数组的实际大小//sizeof((char*)arrU8)，把一个u8 * 转成 char *，在32位机器上结果是4,64位机器上是8//sizeof((char*)arrU8)是输出一个指针的大小//要打印u8类型的数组，直接arrU8就可以了，不用加(char*);printf("---------------------------------------------\n");char arrCh[12] = {0};printf("printf arrCh[12] by arrCh = %s\n", arrCh);//printf arrCh[12] by arrCh = printf("printf arrCh[12] by (char*)arrCh=%s\n", (char*)arrCh);//printf arrCh[12] by (char*)arrCh=printf("sizeof(arrCh)=%d\n", sizeof(arrCh));//sizeof(arrCh)=12printf("sizeof((char*)arrCh)=%d\n", sizeof((char*)arrCh));//sizeof((char*)arrCh)=8printf("strlen(arrCh)=%d\n", strlen(arrCh));//strlen(arrCh)=0printf("strlen((char*)arrCh)=%d\n", strlen((char*)arrCh));//strlen((char*)arrCh)=0memcpy(arrCh, "987", 3);printf("---------------------------------------------\n");printf("printf arrCh[12] by arrCh = %s\n", arrCh);//printf arrCh[12] by arrCh = 123456789printf("printf arrCh[12] by (char*)arrCh=%s\n", (char*)arrCh);//printf arrCh[12] by (char*)arrCh=123456789printf("sizeof(arrCh)=%d\n", sizeof(arrCh));//sizeof(arrCh)=12printf("sizeof((char*)arrCh)=%d\n", sizeof((char*)arrCh));//sizeof((char*)arrCh)=8printf("strlen(arrCh)=%d\n", strlen(arrCh));//strlen(arrCh)=9printf("strlen((char*)arrCh)=%d\n", strlen((char*)arrCh));//strlen((char*)arrCh)=9printf("---------------------------------------------\n");printf("arrU8=%s strlen(arrU8)=%d\n", arrU8, strlen(arrU8));memset(arrU8, 0, sizeof(arrU8));//初始化的时候用sizeofmemcpy(arrU8, arrCh, strlen(arrCh));//复制的时候strlenprintf("arrU8=%s strlen(arrU8)=%d\n", arrU8, strlen(arrU8));printf("---------------------------------------------\n");printf("arrU8=%s strlen(arrU8)=%d\n", arrU8, strlen(arrU8));memset(arrU8, 0, sizeof(arrU8));memcpy(arrU8, "54321", 5);printf("arrU8=%s strlen(arrU8)=%d\n", arrU8, strlen(arrU8));printf("---------------------------------------------\n");printf("arrCh=%s strlen(arrCh)=%d\n", arrCh, strlen(arrCh));memset(arrCh, 0, sizeof(arrCh));memcpy(arrCh, arrU8, strlen(arrU8));printf("arrCh=%s strlen(arrCh)=%d\n", arrCh, strlen(arrCh));exit(0);
}

printf arrU8[12] by arrU8 = 
printf arrU8[12] by (char*)arrU8=
sizeof(arrU8)=12
sizeof((char*)arrU8)=8
strlen(arrU8)=0
strlen((char*)arrU8)=0
---------------------------------------------
printf arrU8[12] by arrU8 = 123456789
printf arrU8[12] by (char*)arrU8=123456789
sizeof(arrU8)=12
sizeof((char*)arrU8)=8
strlen(arrU8)=9
strlen((char*)arrU8)=9
---------------------------------------------
printf arrCh[12] by arrCh = 
printf arrCh[12] by (char*)arrCh=
sizeof(arrCh)=12
sizeof((char*)arrCh)=8
strlen(arrCh)=0
strlen((char*)arrCh)=0
---------------------------------------------
printf arrCh[12] by arrCh = 987
printf arrCh[12] by (char*)arrCh=987
sizeof(arrCh)=12
sizeof((char*)arrCh)=8
strlen(arrCh)=3
strlen((char*)arrCh)=3
---------------------------------------------
arrU8=123456789 strlen(arrU8)=9
arrU8=987 strlen(arrU8)=3
---------------------------------------------
arrU8=987 strlen(arrU8)=3
arrU8=54321 strlen(arrU8)=5
---------------------------------------------
arrCh=987 strlen(arrCh)=3
arrCh=54321 strlen(arrCh)=5